2,4,5-substituted n-oxy and hydroxyimidazoles

ABSTRACT

Dihydroimidazoles having tertiary carbon atoms in the number 4 and number 5 positions of the imidazole ring, oxidized ring nitrogen atoms in the form of oxides and hydroxides and a ATTACHED TO THE CARBON ATOM AT THE 2 IMIDAZOLE RING POSITION. The free radical structures are useful as spin labels when bonded to other molecules through the

United States Patent Boocock et al.

[54] 2,4,5-SUBSTITUTED N-OXY AND HYDROXYIMIDAZOLES [72] Inventors: David G. B. Boocock, Palo Alto; Edwin F. Ullman, Atherton, both of Calif [73] Assignee: Synvar Associates, Palo Alto, Calif.

[22] Filed: June 3, 1968 [2i] Appl. No.: 733,820

[52] US. Cl. ..260/309, 252/40l, 260/213,

260/296 AB [5 l Int. Cl. ..C07d 49/36 [58] Field of Search ..260/ 309 [56] References Cited UNITED STATES PATENTS 9/1967 Henry ..260/309 OTHER PUBLICATIONS Karrer, Organic Chemistry, 2nd English Ed., pages 901 to 902, Elsevier Pub. Co. Inc. NY (I946) Houben-Weyl, Methoden der Organischen Chemie, 4th Ed., vol. VIII, pages 346 to 347.

[ 1 Oct. 10,1972

Georg Thieme Verlag, Stuttgart, Germany (1952) Osiecki et al. .loum. Am. Chem. Soc. vol. 90, pages I078 to 1079 Feb. 14, 1968 Primary Examiner-John D. Randolph AttorneyTownsend and Townsend ABSTRACT 0 16111 or -C group attached to the carbon atom at the 2 imidazole ring position. The free radical structures are useful as spin labels when bonded to other molecules through the 12 Claims, No Drawings 2,4,5-SUBSTITUTED N-OXY AND HYDROXYIMIDAZOLFS This invention relates to imidazoles such as described in copending U.S. patent applications, Ser. No. 696,718 now abandoned, filed Jan. 10, 1968 and Townsend and Townsend file No. 3652-8, filed about Apr. 29, 1968, and further characterized by having a carbon atom, bearing a doubly bonded oxygen or nitrogen atom, attached to the carbon atom in the number 2 imidazole ring position and to methods for their preparation.

In its broadest aspect the present invention is directed to novel compounds having the general formula:

each of R R R and R. is an alkyl group, an alkenyl.

group, an alkynyl group, an aryl group, each of about one to 12 carbon atoms or forms part of an alkylene or alkenylene group R,;:R or R -R each alkylene and alkenylene group having about three to carbon atoms. R,, R R and R, are preferably identical and of up to 4 carbon atoms such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl, sec-butyl and tert-butyl;

each of the atom pairs N, -C, and N B is joined by a single or a double bond provided that only when the atom pair N 2 is joined by a single bond, a hydrogen atom is also bonded directly to C A and B are selected from the hydroxyl group and oxygen and hydrogen atoms according to the order of the bond between the atom pairs N,- C and N B as follows:

1. the atom pairs N LC and N B are both joined by single bonds: A and B are both hydroxyl groups;

2. the atom pairs N,; -C and N,- -B are both joined by double bonds: A and B are both oxygen atoms;

3. the atom pair N 2 is joined by a double bond and the atom pair N B is joined by a single bond: A is an oxygen atom an B is selected from the oxygen and hydrogen atoms and the hydroxyl group;

Y is selected from O and NH; and R is selected from OR,, and -NR,,-R,,, with the proviso that each R is independently selected fro hydrogen or an organic radical such as an alkyl or aryl group of up to 30 carbon atoms. Thus R is of similar scope to R, as defined in Ser. No. 696,718 now abandoned, supra and can also include hydrocarbon or non-hydrocarbon functional substituents such as acyl, alkyl or aryl groups substituted with halogen, hydroxyl, alkoxyl, aryloxy, amino, alkyl or arylamino, mercapto, alkyl or arylmercapto, trialkylsilyl, perfluoroalkyl, nitro, carboxyl, hydroxylarnino, nitrile and the like.

Compositions in accordance with the above formula are useful as anti-oxidants. In general, the free radical structures are useful for the measurement of weak magnetic fields by known techniques. In addition, because of their free radical structure the compounds of this invention exhibit electron spin resonance (ESR) and can be used as spin labels for attachment to other molecules such as biologically active molecules. When used for such a purpose it will usually be desirable to select an appropriate functional group as part of R to serve as a handle for bonding or attaching the free radical molecule to the biologically active molecule, or other molecule to be labeled.

It will be apparent to one skilled in this art that the imidazole ring (minus the substituent) attached at the carbon atom in the 2 ring position can have various oxidation states as disclosed by formulas I-V in Ser. No. 696,718 now abandoned, supra. However, for ease of discussion, reference will hereinafier be made to the following formula to characterize the general structure set forth above:

Rz-sl li+ Furthermore the symbol [B] will at times be utilized to represent the aforementioned N,N-dioxy-4,4,5,5- tetraalkyl dihydro-imidazole ring having an open valence at the carbon atom in the number 2 imidazole ring position.

In another aspect, the invention is directed to a novel process for preparing the substituted hydro-imidazoles of formula (1). Thus these novel compounds can be prepared by starting with either imidazoles such as disclosed in Ser. No. 696,718 now abandoned, supra, and having an inert solvent to yield the aforementioned hydroimidazoles having a attached directly to the carbon in the number 2 imidazole ring position. In a preferred aspect, the reac- 'tion is accomplished in the presence of a small amount of basic catalyst.

Thus, the reaction of while the reaction of with an amine (HNR R yields a substituted amide B'J-OR while the reaction of BCN with an amine (HNR R yields NH Bii-NRIR, l0 7 The general formula for each of these reactions is as follows: r-

2) 0 solvent E BHJ-OR- ReOH B -ORn R7OH catalyst BJ-OR; HNRBR: m BJJ NRQRu R1 catalyst (4) solvent. E

BCEN H0011 B- -OR0 catalyst solvent. BCEN HNRQRQ B NR|R| catalyst Typical alcohols for reaction with the aforementioned nitrile or ester to yield a compound defined by I formulas (2) or (4), supra, include the following:

CH OH c n on C l-l CH OH CH OC H,CH OH CH OOCCH OH sucrose cellulose polyvinyl alcohol I cn cn cn cn CHCH CH OH HOCH CH OH omcHzcHoHzcEcH (CH NCH CH CH OH O N-C H OH H ClCH CH CH Ol-l CHHACHOH 00cm m Lemon cal ocll cu on F CCH OH HzOH CHaO CHCHzOH CHiO Typical amines for reaction with the aforementioned nitrile or ester to yield a compound defined by formulas (3) or (5) include the following:

amlnoethyl cellulose It will be apparent to one skilled in this art that the reaction conditions will be most efficient when he reactants are employed in stoichiometric quantities. However, the use of excessive amounts of any reactants will not prevent the reaction from going to completion. Additionally, one skilled in this art will appreciate that reaction temperatures and pressures can be varied broadly although carrying out the reaction under elevated temperatures and atmospheric pressure conditions is preferred.

Suitable basic catalysts are well known to those skilled in this art and include the carbonates such as Example I Formation of lmidazoles Containing a Cyano Group at the 2 Ring Position Starting with the 2 halo compounds of the'U. S. Pat. application, Ser. No. 724,591, now abandoned, the cyano group can be readily substitutedfor the halogen in the aforementioned compounds. The following example is typical of this reaction: 2-Cyano-l ,3-Dioxy-4,4,5 ,5-Tetramethyl-4,5- Dihydroimidazole 2-Bromol ,3'dioxy-4,4,5 ,5-tetramethyl-4,5-

dihydroimidazole (100 mg.), sodium cyanide (300 mg.) and dimethyl formamide (5 ml.) were warmed and shaken. After minutes an equal volume of ether was added and the resulting mixture filtered. The fil- I trate was chromatographed on silica gel (56 .cm. long X 4.5 cm. diam.) using ether as eluent. Thefractions containing the blue-grey band were collected and, evaporated. The residue was recrystallized from benzene/petroleum ether to yield the named compound 29.5 mg. (38 percent yield) m.p. 160. Anal. calculated for C fl N o Yield C,52.73; H.664; N,23.06 percent, Found: C,52.97; H,6.4l; N,23.14 percent. )tmax(KBr) 2240 cm (C I N).

Example ll Conversion of lmidazoles Having Halogen in the 2 Ring Position to Those With an Amino Group at the 2 Position The 2 nitrile compounds readily react with an alcohol (in the presence of a basic catalyst) to yield a NH 2-ii 0R by the equation:

H.011 NH B-CN g B -OR| where R is defined supra. The following example illustrates a typical procedure for the preparation of a compound in which the halogen attached to the Q carbon is first replaced by a cyano and thereafter an alcohol added across the triple bond of the cyano group: Methyl-( l,3-Dioxy-4,4,5,5-Tetramethyl-4,5-Dihydro- 2-lmidazoyl)-Carboximidate A. 2-Bromol ,3-dioxy-4,4,5 ,5-tetramethyl-4,5- dihydroimidazole, sodium cyanide (200 mg.) and methanol (2ml.) were heated with stirring to just below the temperature of methenol reflux. After 30 minutes, ether (3 ml.) was added and the solution filtered. The filtrate was chromatographed on silica gel (47 cm. long X 3 cm. diam.) using ether as eluent. The blue purple band .was collected an'the solvent removed to yield the title compound ([9 mg.) 45 percent mp. -77". Found: C,50.38; H,7.69; N,l9.70;Anal. calculated for CRH15N3O3; C,50.45; l-l,'l.5 3; N,l9.2 percent. m.w. (by mass spectrometry) 214 4, (CHCI 1630 cm." (C'NH).

B. Starting with the 2-cyano imidazoles the following is a typical reaction:

1 7-Ketoandrost-5-ene-3-B-yl 1,-3 ,dioxy-4,4,5,5-

'tetramethyl -4,5-dihydro-2-imidazoyl) carboximidate 0- o I l qill 3 mg. of Z-cyano-l,3+dioxy-4,4,5,5-tetramethyl-4,5- dihydroimidazole in 2 ml. of pyridine was treated with about 20 mg. of sodium hydride and 10 mg. of 3-3- hydroxy-l7-ketoandrost-5-ene. After heating with shaking for 5 minutes, the mixture had turned purple. It was then diluted with water and sufficient acetic acid was added .to neutralize the strong base. The product was isolated by extraction with benzene and chromatography of the extracts. The electron spin resonance spectrum showed a five line pattern having a 7.4 G. (benzene).

Example lll Conversion of lmidazoles having an Ester Group in the 2 Ring Position to those Having an Amido Group in the 2 Ring Position A. l ,3-Dioxy-4,4,5 ,5 -tetramethyl-4,5-dihydro-2- imidazoyl carboxamide 0- I L. l 1,, NH40H OOOCH; CONH: n: l; a:

A solution of methyl l,3-dioxy-4,4,5,5-tetramethyl- 4,5-dihydro-2-imidazoyl carboxylate in concentrated ammonia was boiled for 3 minutes. The solution was then washed with benzene and acidified with acetic acid. After two extractions with chloroform the only.

radical remaining in the aqueous layer was the desired amide. It could be isolated by evaporation of the aqueous layer and extraction of the residue with chloroform. Chromatography of the chloroform extracts yielded the amide, identified by its ESR spectrum gave a typical S-line pattern (a 7.31 G. chloroform).

B. N-Benzyl-l ,3-dioxy-4,4,5,5-tetramethyl-4,5-

dihydro-Z-imidazoyl carboxamide An acetonitrile solution (2 ml) of 3 mg of methyl 1,3-

dioxy-4,4,5,5-tetramethyl-4,5-dihydro-2-imidazoyl carboxylate was heated with one drop of benzylamine for minutes. Evaporation of the mixture and chromatography of the residue yielded the desired amide. a-= 7.31. Gauss (CHCl C. The imidazoyl containing a primary amido group can also be obtained by converting imidazoyls containing a 2 imino group by reactions with a basic catalyst in an aqueous solution as illustrated as follows:

An acetonitrile solution (ml) of 3 mg of 1,3-dioxy- 4,4,5,5-tetramethyl-4,5-dihydro-2-imidazonitrile was heated with one drop of benzylamine for l5 minutes. Evaporation of the mixture and chromatography of the residue yielded the desired amidine A,,= 7.48 Gauss (benzene). iii

In the foregoing examples the symbol has been used to indicate the structure:

y l. A 4,4,5,5-tetra-substituted dihydroimidazole of wherein each of R,, R R and R is a lower alkyl group;

Y is O or NH; and

R is OR or -NR R wherein each R is independently hydrogen or an organic radical.

2. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1, wherein R is alkyl of from one to four carbon atoms, and R is OR wherein R is an organic radical of up to 30 carbon atoms.

3. A 4,4,5,S-tetra-substituted dihydroimidazole in accordance with claim 2, wherein R is hydrogen.

4. A 4,4,5,S-tetra-substituted dihydroimidazole in accordance with claim 1, wherein Il -R is alkyl of from one to four carbon atoms, and R is NR R wherein R is an organic radical of up to 30 carbon atoms.

5. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 4, wherein R is hydrogen.

6. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1, wherein R -R is alkyl of from one to four carbon atoms and Y is O.

7. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1', wherein Y is NH.

8. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1 wherein R is hydrocarbon of up to 30 carbon atorm.

9. A 4,4,5,S-tetra-substituted-l,3-diazole of the formula:

wherein: the bonds to C and C are joined by a divalent radical of the formula:

,1" wherein R -R is a lower alkyl group;

Y is or Nl-l; and

R, is OR. or NR,R,, with the proviso that each R is independently selected from hydrogen or an or anic a ical. l0. 4,4,, -tetra-substituted diazole in accordance with claim 9 wherein, R, -R alkyl of from one to four carbon atoms and R, is -OR wherein R is hydrocarl0 bon of p. qarbqi atoms-V 11. A 4,4,5,5-tetra-substituted-1,3-diazole in accordance with claim 9 wherein, R -R are alkyl of from one to four carbon atoms and R, is NR R wherein 6 is hydrocarbon 92 tfizqearb tatems 12. A 4,4,5,5-tetra substituted-[,3-diazole in accordance with claim 9 wherein, R is hydrogen. 

2. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1, wherein R1 4 is alkyl of from one to four carbon atoms, and R5 is -OR6, wherein R6 is an organic radical of up to 30 carbon atoms.
 3. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 2, wherein R6 is hydrogen.
 4. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1, wherein R1-R4 is alkyl of from one to four carbon atoms, and R5 is -NR6R6, wherein R6 is an organic radical of up to 30 carbon atoms.
 5. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 4, wherein R6 is hydrogen.
 6. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1, wherein R1-R4 is alkyl of from one to four carbon atoms and Y is O.
 7. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1, wherein Y is -NH.
 8. A 4,4,5,5-tetra-substituted dihydroimidazole in accordance with claim 1 wherein R6 is hydrocarbon of up to 30 carbon atoms.
 9. A 4,4,5,5-tetra-substituted-1,3-diazole of the formula: wherein: the bonds to C4 and C5 are joined by a divalent radical of the formula:
 10. A 4,4,5,5-tetra-substituted diazole in accordance with claim 9 wherein, R1-R4 alkyl of from one to four carbon atoms and R5 is -OR6, wherein R6 is hydrocarbon of up to 30 carbon atoms.
 11. A 4,4,5,5-tetra-substituted-1,3-diazole in accordance with claim 9 wherein, R1-R4 are alkyl of from one to four carbon atoms and R5 is -NR6R6, wherein R6 is hydrocarbon of up to 30 carbon atoms.
 12. A 4,4,5,5-tetra substituted-1,3-diazole in accordance with claim 9 wherein, R6 is hydrogen. 